C++ Ray-Tracing in a Weekend by Peter Shirley is a great resource to start learning about ray-tracers and how to implement one, and at the same time providing all the source code in a GitHub repository . You can find more information about his books on ray-tracing techniques with accompanying implementations on his blog, and you can also download the books as .pdf, or load them on your Kindle device for free from the GitHub project.

The main goal of this blog post is not to teach the concepts of ray-tracing, Peter does a great job of that, but provide a walk-through tutorial on how to accelerate practical applications and algorithms using SYCL.